3GPP Long Term Evolution, LTE, is the fourth-generation mobile communication technologies standard developed within the 3rd Generation Partnership Project, 3GPP, to improve the Universal Mobile Telecommunication System, UMTS, standard to cope with future requirements in terms of improved services such as higher data rates, improved efficiency, and lowered costs.
The Evolved Packet Core, EPC, is the core network of the LTE system and is an evolution of the packet-switched architecture used in GPRS/UMTS. The separated sub-domains of previous mobile generations of circuit-switching for voice and packet-switching for data is now realized in the EPC as packet switched architecture only. The main components of the EPC are the Serving Gateway, SGW, the Packet Data Network, PDN, Gateway, PGW, and the Mobility Management Entity, MME.
In an LTE telecommunications network the type of identifiers used for identifying a connected User Equipment, UE, differ between the core network nodes and the LTE radio base stations, eNodeBs, eNBs. The identifier values used for identifying a UE are different in the core nodes and the eNBs. Core nodes typically use long-term values corresponding to the UE's device hardware or SIM card, such as IMSI, MSISDN and IMEI, in the following denoted permanent user equipment, UE, identifiers, IDs. The eNBs are not aware of these identifiers but instead use temporary values corresponding to the temporary connections the eNBs have towards the UE and the core nodes. These temporary UE identifiers may change between eNBs.
Since the LTE eNBs are not aware of the permanent UE IDs used in the core nodes these identifiers may not be used to identify an UE within an eNB. Moreover, a UE identifier used in an eNB is temporary and will change from time to time and between eNBs. Hence, it is not possible to use the permanent UE IDs to trigger functionality in an eNB for a particular UE. However, there are scenarios where there is a need to trigger functionality in an eNB based on a permanent identity.
One such scenario is lawful interception, LI, in cloud networks, whereby operators and Internet service providers are legally obliged to provide traffic data generated from public telecommunications and Internet services for the purpose of detection, investigation and prosecution of crime and criminal offences, including terrorism.
Usually a public official, for instance a judge, is in charge of authorizing investigation on target persons, allowing to activate LI on communications of the target persons or to query data retention databases storing data from user equipment communication. LI implies activating interception on communications directed to/from a user equipment identified as belonging to the target person and/or to retrieve stored communication for an identified user equipment. The service is performed as a UE identity dependent service, based on a permanent identity for UE in the wireless network.
An authorization for investigation on target persons is, however, applicable only in the jurisdiction of the authorizing party. For a scenario of LI in cloud networks, the core nodes of the network may be placed in a different country than the eNBs. Since an authorization to perform LI, only extends to the specific jurisdiction of the authorizing public official, LI information for a specific UE cannot be allowed to be retrieved from or passed to jurisdictions not within the authority of the authorizing public official. Consequently, LI regulations prohibit LI information for a specific UE being passed over country borders, so having LI implemented in the core nodes in one country and intercepting a UE which is served by an eNB in another country is not legal. One possible solution for this is to place LI functionality in the eNBs instead of in the core nodes. However, LI is handled per UE using UE identifiers on a core network level, e.g. IMSI, MSISDN or IMEI. Since these values are not known by the eNBs they can't be used for triggering LI functionality in an eNB for a given UE.